1. Field
The present invention relates to a communication apparatus and a communication method.
2. Description of the Related Art
Heretofore, 1:1 protection has been known as one of the protection functions in networks such as Ethernet (registered trademark). The 1:1 protection is defined as different paths for a network in use and a network in reserve. When trouble occurs in the network in use, the network in reserve is used for transmitting frames and so on. FIG. 38 is a diagram illustrating an exemplary configuration of a communication system 1 which is set to 1:1 protection among the respective communication apparatuses 10 to 30. FIG. 36 illustrates a virtual local area network (VLAN) as an exemplary path.
When the path is configured, for instance, communication apparatuses 10 to 30 may exchange “Operations, Administration, and Maintenance” (OAM) frames, which are also referred to as “Continuity Check Messages” (CCMs), among one another to monitor the VLAN. For example, an exchange of OAM frames between the communication apparatus 10 and the communication apparatus 20 allows the communication apparatus 10 and 20 to monitor the working VLAN and the backup VLAN between the communication apparatuses 10 and 20. Hereinafter, this kind of the monitoring will be referred to as “individual VLAN monitoring”. Likewise, the exchange of OAM frames allows the communication apparatuses 10 and 20 to monitor two VLANs, the working VLAN and the backup VLAN, between the communication apparatuses 10 and 20. Hereinafter, this kind of monitoring will be referred to as “service monitoring”.
The OAM frame distinguishes between the individual VLAN monitoring and the service monitoring by monitoring levels. In the example illustrated in FIG. 36, the monitoring level of the individual VLAN monitoring is “K” and that of the service monitoring is “K+1”. The service monitoring observes a wider (or longer) section compared with the individual VLAN. Thus, the service monitoring is provided with a higher level than that of the individual VLAN.
FIG. 37A and FIG. 37B are diagrams illustrating exemplary formats of the respective frames, a data frame in FIG. 37A and an OAM frame in FIG. 37B. As illustrated in FIG. 37B, the OAM frame includes a “monitor level”. For example, the monitor level “K” or “K+1” may be inserted in the OAM frame. The “monitoring levels” included in the OAM frames allow the communication apparatuses 10 to 30 to determine the respective monitoring levels of the OAM frames.
The process for receiving the OAM frame or the like in each of the communication apparatuses 10 to 30 will be described. FIG. 38 is a diagram illustrating en exemplary reception processing in the communication apparatus 20. The communication apparatus 20 is connected to the opposite communication apparatus 10 through two paths, the working VLAN and the backup VLAN. Here, a line card #1 (260) is employed for the connection with the working VLAN and a line card #2 (270) is employed for the connection with the backup VLAN. In addition, the communication apparatus 20 is also connected to the communication apparatus 30 through the working VLAN and the backup VLAN. In this case, a line card #3 (280) is employed for the connection with the VLAN in use and a line card #4 (290) is employed for the connection with the backup VLAN.
The line card #1 (260) receives frames from the communication apparatus 10 through the working VLAN. An OAM extractor 262 of the line card #1 (260) outputs OAM frames of the monitoring level “K” among the received frames and the remainder is output to a transfer processor 263. A failure monitor 261 may verify the continuity of the OAM frames of the monitoring level “K” to monitor the working VLAN, which is connected to the communication apparatus 10. The communication apparatus 20 receives frames transmitted from the communication apparatus 10 through the backup VLAN. An OAM extractor 272 of the line card #2 (270) outputs OAM frames of the monitoring level “k” to a failure monitor 271 and outputs other OAM frames to a transfer processor 273. The failure monitor 271 may verify the continuity of the above OAM frames to monitor the backup VLAN.
When the working VLAN is in a normal state, the OAM frame of the monitoring level “K+1” received through the working VLAN is output from the transfer processor 263 to the line card #3 (280). When a failure or the like has occurred on the working VLAN, the pass is switched to the backup VLAN. An OAM frame of the monitoring level “K+1” received through the backup VLAN is output from the transfer processor 273 to the line card #3 (280).
The OAM extractor 282 of the line card #3 (280) outputs OAM frames of the monitoring level “K+1” to a failure monitor 281 and outputs other OAM frames to the working VLAN. The failure monitor 281 may monitor both the working VLAN and the backup VLAN (service monitoring). This is because the failure monitor 281 has an ability of receiving service-monitoring OAM frames (e.g., those of the monitoring level “K+1”) even in either the case of the working VLAN in active state or the case of the backup VLAN in the active state.
On the other hand, when a failure or the like occurs in the working VLAN between the communication apparatus 20 and the communication apparatus 30, the path to the communication apparatus 30 is changed from the working VLAN to the backup VLAN. FIG. 39 is a diagram illustrating an exemplary process for receiving an OAM frame. The transfer processor 263 of the line card #1 (260) changes the destination of a frame from the line card #3 (280) to the line card #4 (290) upon detecting a failure in the working VLAN (e.g., one with VLAN ID=A) between the communication apparatuses 20 and 30. Therefore, the frame is transmitted to the communication apparatus 300 through the backup VLAN (e.g., one with VLAN ID=B).
Furthermore, 1+1 protection is also known as a protection function in a network. The 1+1 protection is a protection function that allows frames to be transmitted to both the working path and the backup path.
As a technology for the 1+1 protection, for example, a working monitoring frame and a backup monitoring frame are transmitted from a switch device on a transmitting side to both the working path and the backup path. Then, a switch device on a receiving side discards the backup-monitoring frame from the working path, while discarding the working-monitoring frame from the backup path. The transmitted working-monitoring frame and the transmitted backup monitoring frame are used for confirming communication through the respective paths.
Japanese Unexamined Patent Application Publication No. 2009-152729, ITU-T G.8031, IEEE 802.1ag, and ITU-T Y.1731 are examples of the related art.